Gamma value is an important parameter of a display device to characterize a non-linear relationship between luminance of an image displayed on the display device and an input signal voltage. For a display device, the luminance of the image displayed on the display device varies exponentially with the input signal voltage, resulting that a dark area in the displayed image is darker than that in an actual image and a bright area in the displayed image is brighter than that in the actual image, that is to say, the display device performs compression on the dark area of the actual image and extension on the bright area of the actual image.
Similarly, the human eyes' sensitivity to different luminance of the light is also non-linear, but the human eyes' sensitivity is high to the low luminance and is low to the high luminance, that is to say, the human eyes perform extension on the dark area of a actual scene and compression on the bright area of the actual scene, which exactly is opposite to the luminance response of the display device to the actual image. Therefore, Gamma curve (a curve to which Gamma value corresponds) of the display device can be adjusted to conform to the standard for Gamma 2.2 curve, the luminance of the image displayed by the display device which conforms to such a standard will be linearly perceived in the human eyes approximately, and thus a better display effect can be obtained.
In the prior art, in order to test whether Gamma curve of a display device manufactured conforms to the standard for Gamma 2.2 curve, a special optical equipment (for example, color analyzer) is adopted to test the luminance value output from the display device under each of grayscale voltages, a curve formed by a plurality of pairs of input grayscale voltages and output luminance values on a coordinate plane is compared with the Gamma 2.2 curve, and a reference voltage of the display device is adjusted when the curve thus formed does not conform to the standard for Gamma 2.2 curve, such that the Gamma curve of the display device conforms to the standard for the Gamma 2.2 curve. However, in the prior art, it needs a special optical equipment to be used to test the Gamma curve of the display device by means of the above method for measuring the Gamma value of the display device, so the above method for measuring the Gamma value of the display device is complicated and the test efficiency is low.